System and method for image stabilization in videoconferencing

ABSTRACT

A terminal comprises a display substrate and an actuator configured to move the display substrate in a cyclic movement over a viewing area. A proximity sensor is configured to generate detection signals. An image controller, configured to receive the detection signal, calculates a cycle time of the cyclic movement of the display substrate and controls at least one of a transmission rate of the display data to the display substrate and the movement of the display substrate caused by the actuator.

TECHNICAL FIELD

The disclosure is directed, in general, to a videoconferencingtechnique.

BACKGROUND

This section introduces aspects that may be helpful in facilitating abetter understanding of the disclosure. Accordingly, the statements ofthis section are to be read in this light and are not to be understoodas admissions about what is in the prior art or what is not in the priorart.

Communication via computer networks frequently involves far more thantransmitting text. Computer networks, such as the Internet, can also beused for audio communication and visual communication. Still images andvideo are examples of visual data that may be transmitted over suchnetworks.

One or more cameras may be coupled to a personal computer (PC) toprovide visual communication. The camera or cameras can then be used totransmit real-time visual information, such as video, over a computernetwork. Dual transmission can be used to allow audio transmission withthe video information. Whether in one-to-one communication sessions orthrough videoconferencing with multiple participants, participants cancommunicate via audio and video in real time over a computer network(i.e., voice-video communication). Typically the visual imagestransmitted during voice-video communication sessions depend on theplacement of the camera or cameras.

SUMMARY

One aspect provides an apparatus. In one embodiment, the apparatusincludes: a display substrate occupying less than an entirety of aviewing area and configured to display display data; an actuatorconfigured to move the display substrate in a cyclic movement over theviewing area; a proximity sensor assembly configured to generate, atleast once during a cycle of the movement of the display substrate, adetection signal; and an image controller configured to receive thedetection signal generated by the proximity sensor assembly, calculate acycle time of the cyclic movement of the display substrate and generatea command to control at least one of a transmission rate of the displaydata to the display substrate and the movement of the display substratecaused by the actuator.

In another aspect, a method for image stabilization in videoconferencingis disclosed. In one embodiment, the method includes: moving a displaysubstrate in a cyclic movement over a viewing area and displaying adisplay data, the display substrate occupying less than an entirety ofthe viewing area; generating by a proximity sensor assembly, at leastonce during a cycle of the movement of the display substrate, adetection signal; receiving by an image controller the detection signalgenerated by the proximity sensor assembly; calculating a cycle time ofthe cyclic movement of the display substrate; and controlling at leastone of a transmission rate of the display data to the display substrateand the movement of the display substrate caused by the actuator.

BRIEF DESCRIPTION OF THE DRAWINGS

Reference is now made to the following descriptions taken in conjunctionwith the accompanying drawings, in which:

FIG. 1 illustrates a schematic representation of an embodiment of avideoconferencing terminal, in which the principles of the disclosuremay be implemented;

FIG. 2 illustrates a schematic representation of certain elements of anembodiment of a videoconferencing terminal constructed according to theprinciples of the disclosure;

FIG. 3 illustrates a schematic representation of certain elements ofanother embodiment of a videoconferencing terminal constructed accordingto the principles of the disclosure;

FIG. 4 illustrates a schematic representation of certain elements of yetanother embodiment of a videoconferencing terminal constructed accordingto the principles of the disclosure;

FIG. 5 a and FIG. 5 b illustrate schematic representations of certainelements of some embodiments of a videoconferencing terminal constructedaccording to the principles of the disclosure; and

FIG. 6 illustrates a flow diagram of one embodiment of a method forimage stabilization in a videoconferencing terminal carried outaccording to the principles of the disclosure.

DETAILED DESCRIPTION

The present disclosure relates in particular to stabilizing imagedisplay in a videoconferencing terminal (or apparatus).

Some description of a videoconferencing terminal with a persistence ofvision display and a method of operation thereof to maintain eye contactmay be found in U.S. patent application Ser. No. 12/640,998, entitled“Videoconferencing Terminal With A Persistence Of Vision Display And AMethod Of Operation Thereof To Maintain Eye Contact,” filed on Dec. 17,2009, by Cristian A. Bolle, et al., and published as U.S. PublicationNo. 2011/0149012, the content of which is incorporated herein byreference in its entirety.

The videoconferencing terminals can display an image by employing anarray of electronic light sources (e.g., red, green and bluelight-emitting diodes (LEDs)) spun at a speed large enough such that thehuman eye can not follow the motion and will see a continuous image. Ifthe electronic light sources are modulated in a synchronized way at evenhigher speed, an image can be displayed. For example, the electroniclight sources may be rotated at a speed for an image repetition of 60 Hzand modulated at a speed of 1 MHz. A camera can then be located behindthe electronic light sources that allows a video conference participantto establish eye contact by looking through the front of the terminal tothe camera instead of, for example, looking at a camera mounted on thetop or side of the terminal.

A display substrate is used to provide a persistence of vision display.The shape or type of display substrate may vary and may be based on thegeometry of the viewing area of a particular videoconferencing terminal.For example, the display substrate includes a wheel with one or morevanes (or arms) extending from a center. The wheel is configured tocarry on the front of each arm a necessary array of electronic lightsources to accurately display an image while the structure is rotated byan actuator (e.g., a motor that may be centrally mounted with respect toa viewing area). As indicated above, an image repetition rate of 60 Hzmay be used with the image repetition rate needing to be greater than 30Hz. For a single arm at 30 Hz, the rotation speed of the arm translatesto 1800 RPM. The rotation speed can be reduced proportionally to thenumber of arms that may be used to provide the display. An imagerepetition rate greater than a 100 Hz can be used to provide a higherquality display.

Any additional electronics needed to drive the electronic light sourcescan be advantageously mounted on the back of each arm and out of sightfrom a local participant. Power to drive the electronic light sourcesmay be transferred over the shaft of the motor by a set of brushes or acoaxial transformer.

The display substrate can provide images of a remotely locatedvideoconference participant while a camera (e.g., a video camera)mounted behind the spinning wheel captures images of a localvideoconference participant through open areas associated with thespinning wheel. By having the camera located behind the displaysubstrate and looking therethrough, both videoconference participantscan establish eye contact and enhance the feeling of intimacy in thecommunication.

FIG. 1 is a schematic view of an embodiment of a videoconferencingterminal 100, constructed according to the principles of the disclosure.The videoconferencing terminal 100 is configured to simultaneouslycapture a camera image and provide a display image. Thevideoconferencing terminal 100 includes a display substrate 110, anactuator 120 and a camera 130. Additionally, the videoconferencingterminal 100 may include additional components typically included in aconventional videoconferencing terminal. For example, thevideoconferencing terminal 100 may include a microphone, a speaker and acontroller that directs the operation of the videoconferencing terminal100. The microphone and speaker may be associated with the controller.In some embodiments, the videoconferencing terminal 100 may include asection that is a partially evacuated volume in which the displaysubstrate 110 operates.

The display substrate 110 includes a substrate 112 having an array ofelectronic light sources 114 located thereon. The array 114 may be asingle column array as illustrated or may include multiple columns. Thearray of electronic light sources 114 is sized to provide a persistenceof vision display in a viewing area 140 when the display substrate 110is moved over the viewing area 140. As such, the number of rows of thearray of electronic light sources 114 may be equivalent or substantiallyequivalent to the radius (r) of the viewing area 140. The viewing area140 may coincide with a substantial transparent substrate that is placedin front of the videoconferencing terminal 100 (i.e., opposite side ofthe display substrate 110 from the camera 130). The display substrate110 occupies less than an entirety of the viewing area 140. Thus, thedisplay substrate 110 is smaller than the viewing area 140. Accordingly,persistence of vision is relied on to provide a display image for thevideoconferencing terminal 100.

The display substrate may be caused to move (e.g. rotate) by way of anactuator 120 located at a suitable position.

The videoconferencing terminal 100 also includes electronic circuitry113 coupled to the array of electronic light sources 114. The electroniccircuitry 113 is configured to control the array of electronic lightsources 114 to form the display image. The electronic circuitry 113 maybe located at any suitable position.

The electronic circuitry 113 is configured to direct the operation ofeach of the electronic light sources of the array 114. The electroniccircuitry 113 may include a matrix of thin film transistors (TFT) witheach TFT driving and/or controlling a particular electronic light sourceof the array 114. The electronic circuitry 113 may include componentstypically employed in a conventional array-type active backplane. In oneembodiment, the electronic circuitry 113 may operate similar to anactive backplane employed in a conventional LED display. However otherknown display elements may likewise be used. Power to drive theelectronic light sources 114 (and the electronic circuitry 113) may betransferred over a shaft of the actuator by known means such as a set ofmechanical brushes or through magnetic induction, for example in theform of a coaxial transformer.

Therefore, as described in relation to the embodiment of FIG. 1, animage of a remote object, e.g. a videoconference participant, may bedisplayed on the viewing area of the videoconferencing terminal as thedisplay substrate moves (e.g. rotates) at a predetermine speed.

However, the speed of movement (e.g. rotation) of the display substratemay have direct effect on the appearance of the image on the displaysubstrate. Indeed, if fluctuations are present in the speed of movementof the display substrate 110, the image may be displayed distorted or atleast unstable to the human eye.

As the movement of the display substrate 110 is caused by a mechanicallydirected action of the actuator 120, it may in practice occur that suchmechanical activation is not always stable. Lack of stability may occur,for example, due to fluctuations in the power supplied to the actuator,the manner in which power is applied to the actuator (e.g. powering bysudden pulses may typically cause more fluctuations as compared to acontinuous smooth supply) or the manner in which the speed of theactuator is controlled. As previously mentioned, such lack of stabilitymay cause distortion or instability in the image displayed. Therefore,it is desirable to provide a videoconferencing terminal with provisionsdirected to maintaining the displayed image stable, or at least reducingthe effects of fluctuations in the speed of the display substrate, as itmoves, on the displayed image.

According to the present disclosure, use is made of a proximity sensorassembly and an image controller which, in cooperation, allow forcontrolling the transmission rate of the display data to the displaysubstrate or the movement of the display substrate caused by theactuator, thereby maintaining or improving the stability of thedisplayed image.

The image controller may be located at any convenient position. In someembodiments, the image controller may be located at a fixed position. Insome alternative embodiments, the image controller may be located on thebody of the display substrate as will be described further below.

In some embodiments, the proximity sensor assembly may be a combinationof an optical emitter or an optical receiver. In other embodiments theproximity sensor assembly may comprise magnetic elements.

Referring now to FIG. 2, certain elements of a videoconferencingterminal are shown according to some embodiments. Display data D useablefor displaying an image of a remote object may be received by thevideoconferencing terminal and stored in a data storage module 210. Thisdata D is intended to be transferred to the display substrate 240.Though not illustrated in FIG. 2, the display substrate 240 similarlyincludes electronic circuitry and electronic light sources as discussedwith respect to the display substrate 110 of FIG. 1. Thevideoconferencing terminal further comprises an image controller 220. Insome embodiments the image controller 220 is in charge of generatingcommands for triggering or adjusting the transmission rate of thedisplay data D from the data storage module 210 to the display substrate240 through a data link 230. In some embodiments the image controller220 is in charge of generating commands to adjust the speed of movementof the actuator. In some embodiments the image controller 220 is incharge of both generating commands for triggering or adjusting thetransmission rate of the display data D from the data storage module 210to the display substrate 240 and generating commands to adjust the speedof movement of the actuator.

Once the display data D is received at electronic circuitry coupled tothe display substrate 240, the electronic circuitry may drive the lightsources (as described with reference to the electronic circuitry 113FIG. 1) causing the light sources to display the image concerned.

According to some embodiments of the present disclosure, an opticalemitter may be mounted at a suitable location on the display substrate.In the embodiment of FIG. 2, an optical emitter 250 is shown to bemounted on the rear surface (the surface opposite to the image displaysurface) of the display substrate 240. The optical emitter 250 isconfigured to emit an optical signal 260.

Further, an optical receiver 270 may be installed at a location suitablefor receiving the optical signal 260 from the optical emitter 250, asshown in the embodiment of FIG. 2. The optical receiver 270 may receivethe optical signal 260 during an optical coupling period in which themovement of the display substrate 240 causes the optical emitter 250 toestablish optical coupling (optical contact) with the optical receiver270, thereby allowing the latter to receive the optical signal 260. Theposition in which the optical coupling occurs is schematically shown inFIG. 2 by reference P.

Upon receipt of the optical signal 260 by the optical receiver 270, thelatter may generate a detection signal 280 which is input into the imagecontroller 220. As the display substrate 240 moves (e.g. rotates asshown by arrow A) away from position P, the optical coupling between theoptical emitter 250 and the optical receiver 270 is interrupted (seee.g. the display substrate shown by of broken lines in FIG. 2). Theinterruption of the optical coupling continues until the displaysubstrate 240 completes a cycle and arrives back to the position P whereoptical coupling is again established. At this occurrence, the opticalreceiver 270 may generate a second (subsequent) detection signal 280which is again input into the image controller 220.

Based on the reception of the first detection signal and the subsequentdetection signal, the image controller 220 may calculate a cycle timerelative to the cyclic movement of the display substrate 240. Preferablythe cycle time calculated may then be divided into a number of radialimage lines that form a complete screen of the image to be displayed.The number of radial image lines may vary according to the specific use,in one embodiment the number of radial image lines may be 1024, andother values may be envisaged which may be determined by therelationship 2πN, where N is the number of radial pixels (i.e.electronic light sources present on the display substrate). The numberof image lines may be selected to be higher, by choosing a higher valuefor N (higher than the number of electronic light sources), thisoversampling may be useful in order to enhance image quality.

The resulting value may then be compared to a predetermined target valuewhich is one that is considered to provide an acceptable image display.In case the comparison shows a deviation from the predetermined targetvalue, the image controller may generate:

-   -   a command transmitted to a driving circuitry (not shown) of the        actuator 120 thereby causing the driving circuitry to adjust the        speed of the actuator and as a consequence, adjust the movement        of the display substrate 240 so as to display the image without,        or substantially free of, instability effects; or    -   a command transmitted to a line data transmission unit, for        example a known transmitter (not shown) thereby causing the line        data transmission unit to adjust the transmission rate sent to        the display substrate 240 and as a consequence, adjust the        display rate of the display substrate 240 so as to display the        image without, or substantially free of, instability effects.

The line data transmission may be adjusted in conformity with thecalculated cycle time of the last cyclic movement. Alternatively, theline data transmission may be adjusted in conformity with the calculatedcycle time obtained from a number of the last (most recent) cyclicmovements. For example, an average value or a predictive algorithm maybe employed that calculates a cycle time based on the values of the mostrecent cycle times.

Advantageously, the image controller also predicts the next cycle timeand adjusts the line data transmission rate based on, or having regardto, such prediction.

The image controller 220 and other image controllers disclosed hereinmay be any known processing unit such as for example an FPGA, suitablyprogrammed.

The optical emitter 250 may comprise one or more sources of emission ofoptical signal (including a plurality of optical emitters). Likewise,the optical receiver 270 may comprise one or more elements of receptionof optical signal (including a plurality of optical receivers).Therefore, in some embodiments more than one optical receivers mayreceive optical signal from one or more optical emitters. Thispossibility may be advantageous in cases where feedback information (inaddition to the optical coupling information as described above) needsto be exchanged between the moving parts (including but not limited tothe display substrate and any parts involved in conveying movements fromthe actuator to the display substrate) and the fixed parts (includingbut not limited to videoconferencing data transmitter and imagecontroller). One example of exchange of such feedback information may beinformation related to the temperature of the moving parts in order toavoid overheating. Another example of such feedback information may beinformation received from a user interface. For example, thevideoconferencing terminal may comprise a touch-sensitive screen and thedisplay substrate may comprise detectors that can detect changes as auser touches the screen. The use of touch-sensitive screen is disclosedin the above-referenced document published as U.S. Publication No.2011/0149012. Therefore, the feedback information detected by thedetectors may be provided to other parts of the videoconferencingterminal or other equipment in the videoconferencing network.

In such cases, one optical emitter may transmit an optical signal to anoptical receiver in an operation for maintaining the display imagestabilized (as already discussed with reference to FIG. 2), and anotheroptical emitter may transmit to a second receiver, feedback informationfor example related to the temperature status of one or more movingparts by way of another optical signal. Other combinations of exchangeof feedback information may also be envisaged within the scope of thepresent disclosure.

According to some alternative embodiments, the optical emitter may bealso located at a fixed position (as opposed to being installed on thedisplay substrate and thus being movable). FIG. 3 illustrates aschematic representation of certain elements of a videoconferencingterminal constructed according to this alternative embodiment. In FIG.3, unless otherwise provided, like elements have been given likereference numerals as those of FIG. 2.

Referring to FIG. 3, the characteristics and functionalities of certainelements of the videoconferencing terminal such as those of the datastorage module 210, the image controller 220 and the data link 230 aresimilar to those described in relation to the embodiments of FIG. 2.Therefore, further description related to these elements is considerednot necessary.

According to the embodiment of FIG. 3, and differently from that of FIG.2, an optical emitter 251 is mounted at a suitable fixed location, asshown. The optical emitter 251 is configured to emit an optical signal260.

An optical receiver 270 is installed at a location suitable andpreferably optically aligned with the optical emitter 251 for receivingthe optical signal 260, as shown in the embodiment of FIG. 3. However,differently from the embodiment of FIG. 2, the optical receiver 270 mayreceive the optical signal 261 continuingly during a major period of thecyclic movement of the display substrate 240 as shown by solid lines(arrow A shows the direction of movement). Thus, due to the existence ofoptical alignment between the optical receiver 270 and the opticalemitter 251 and the absence of an obstacle on an optical coupling pathbetween these two elements during a major period of the cyclic movementof the display substrate 240, the optical signal is continuouslyreceived by the optical receiver 270 until it is interrupted at aninstant at which the display substrate 240 enters into a position inwhich it blocks the coupling path of the optical signal 260 between theoptical emitter 251 and the optical receiver 270. This blocking positionis schematically shown in FIG. 3 by reference P and the displaysubstrate 240 is shown by way of broken lines.

Upon receipt of the optical signal 260 by the optical receiver 270, thelatter generates a detection signal 281 which is input into the imagecontroller 220. As the display substrate 240 moves (e.g. rotates) to theblocking position P, the optical coupling between the optical emitter251 and the optical receiver 270 is interrupted. The interruption ofsaid optical coupling causes the optical receiver 270 to stop generatingthe detection signal 281. As the display substrate 240 continues itsmovement, thus leaving position P, the blocking of the optical signal260 by the display substrate 240 terminates and the optical coupling isreestablished between the optical emitter 251 and the optical receiver270. This situation continues until the display substrate 240 completesa cycle and arrives back to the position P where optical coupling isagain blocked. At this occurrence, the optical receiver 270 once againstops the generation of a detection signal 281 which is input into theimage controller 220.

The image controller 220 may be programmed to calculate a cycle timerelative to the cyclic movement of the display substrate 240, based onthe occurrence of the first interruption and the subsequent interruptionof the detection signal 281. Once the cycle time has been calculated,the procedure for stabilizing the display image on the videoconferencingterminal is followed in a similar manner as that described withreference to FIG. 2.

The optical emitter 250 or 251 may be any known device suitable for thespecific operation. For example, the optical emitter 250 may be acollimated infrared light source.

The optical receiver 270 may be any known device suitable for thespecific operation. For example, the optical receiver 270 may be alensed infrared detector with a Schmidt trigger logic.

FIG. 4 illustrates a representation of certain elements of analternative embodiment of a videoconferencing terminal constructedaccording to the principles of the invention. In FIG. 4, like elementshave been given reference numerals baring the same last two digits asthose of FIG. 2 (e.g. element 220 in FIG. 2 is similar to element 420 inFIG. 4). Unless otherwise provided, the principles of operation of thevideoconferencing terminal of FIG. 4 are similar to those of theterminal of FIG. 2, for which further description is considered notnecessary. The embodiment of FIG. 4 differs however from the embodimentof FIG. 2 in that instead of the use of an optical emitter and anoptical receiver as a proximity sensor assembly in FIG. 2, in theembodiment of FIG. 4 use is made of magnetic detection as will bedescribed below.

Referring back to FIG. 4, the videoconferencing terminal according tothe present embodiment comprises a magnetic proximity sensor assemblycomprising a combination of a magnetic detector 470 such as for examplea solenoid and a magnetic booster piece 450 which may be made forexample of a metal capable of causing induction, such as iron. In someembodiments, the magnetic detector 470 may be located at a fixedposition and the magnetic booster piece 450 may be placed on the body ofthe display substrate 440. With this arrangement, as the displaysubstrate 440 moves in cyclic movement (e.g. rotates), at a certainmoment in the cyclic movement of the display substrate 440, the magneticbooster piece 450 approaches the magnetic detector 470. This is shown inFIG. 4 at position P relative to the movement of the display substrate440. The movement of the magnetic booster piece 450 in proximity to themagnetic detector 470 induces a change in the magnetic field present inthe magnetic detector 470. This effect is schematically represented inFIG. 4 by arrows 460.

The change in the magnetic field in the magnetic detector 470 may beconverted into an electric signal 480 which constitutes a detectionsignal that is then input in the image controller 420. This may be donefor example by a current which is induced in the solenoid of themagnetic detector 470 as is known in the art.

From this point on, the operation of the image controller and otherelements of the terminal of FIG. 4 are substantially similar to those ofFIG. 2.

In some embodiments, the magnetic booster piece may be located at afixed position and the magnetic detector may be placed on the body ofthe display substrate. With this arrangement (not shown), as the displaysubstrate moves in cyclic movement (e.g. rotates), at a certain momentin the cyclic movement of the display substrate, the magnetic detectorapproaches the magnetic booster piece. The movement of the magneticdetector in proximity to the magnetic booster piece induces a change inthe magnetic field present in the magnetic detector. The change in themagnetic field in the magnetic detector may be converted into anelectric signal which constitutes a detection signal that is then inputin the image controller (which may be also located on the displaysubstrate).

From this point on, the operation of the image controller and otherelements of the terminal of FIG. 4 are substantially similar to those ofFIG. 2.

As mentioned above, the image controller may be located at anyconvenient position. In some embodiments, the image controller may belocated at a fixed position. In some alternative embodiments, the imagecontroller may be located on the body of the display.

In case the image controller is located at a fixed position, thecommands generated by the image controller, either transmitted to adriving circuitry or transmitted to a line data transmission unit(generally referred to as commands) may be conveyed to a destinationusing any known means, for example by a simple wiring connection.

Alternatively, in case the image controller is located on the body ofthe display substrate, the commands generated by the image controllermay be transmitted to an appropriate destination using an optical linkor a radio link as will be described with reference to FIG. 5 a and FIG.5 b respectively.

Referring to FIG. 5 a, a display substrate 510 is illustrated which isconfigured to undergo a cyclic movement caused by the operation of anactuator 540 as already described. The movement generated by theactuator is transferred to the display substrate 510 by known means,such as for example a shaft 550 as shown in FIG. 5 a. A proximity sensorassembly, generally shown by reference numeral 520, is configured togenerate a detection signal as already described with reference to theembodiments of FIGS. 2, 3 and 4. Thus the proximity sensor assembly 520may operate using optical means or magnetic means. The proximity sensorassembly 520 comprises a first detection element 521 and a seconddetection element 522. The detection signals (as described above) may begenerated by the first detection element 521 of the proximity sensorassembly 520 which is located on the body of the display substrate 510.

An image controller 530 is located on the display substrate 510.Preferably the image controller 530 is located at a central part of thedisplay substrate 510 as shown in FIG. 5 a. Detection signals generatedby the proximity sensor assembly 520 may be input from the firstdetection element 521 into the image controller 530 by known means suchas wires (not shown).

Once the detection signals are received by the image controller 530, thelatter may calculate the cycle time and thereafter generate theadjustment commands in order to display the image without, orsubstantially free of, instability effects as described above.

In the embodiment of FIG. 5 a, said commands may be transmitted from theimage controller 530 by way of an optical link. An optical emitter 560may be located at a convenient location on the display substrate 510.Preferably the optical emitter 560 is located at a central locationrelative to the display substrate 510 as shown in FIG. 5 a. Furthermore,an optical receiver 580 is located at a convenient location so as toreceive an optical signal 570 transmitted from the optical emitter 560.Preferably shaft 550 has a through-hole 551 present across alongitudinal axis thereof, thereby allowing for a passage of the opticalsignal through the longitudinal hole 551 and reach the optical receiver580 as shown in FIG. 5 a. Upon receiving the optical signal 570, theoptical receiver 580 may then convert the received signal intoappropriate signal formats, e.g. an electric signal, which may be usedfor any adjustments required in the speed of rotation of the actuator540 or the transmission rate of the display data.

Commands generated by the image controller 530 may be converted intooptical signals by known means such as for example a light emittingdiode (LED), or the like.

Preferably a storage unit (not shown), e.g. a memory, may be used tostore compressed or raw image data on the moving part. Compressed imagedata, known in the art, is an image that has been processed to reducethe image file size by sacrificing some of the image details. Image datamay be stored and transmitted in various formats for example as twodimensional RGB pixel arrays (Raw data), as multiple line data to beused to directly generate line commands (also a form of raw data), andboth can also be compressed using standard techniques such as run lengthencoding (RLE), jpeg or motion jpeg depending on the computing power ofthe image controller. A raw image may be an image that has not beenprocessed. In such cases, the optical emitter 560 may transmit thecompressed or raw image data, preferably, at a lower data rate thanneeded by the moving display substrate. The image controller mounted onthe display substrate (thus movable) may then process this data andgenerate commands to adjust the line data to be fed to the light sourcesas needed. Transmitting at a lower rate may have the advantage ofrequiring less expensive hardware for the transmission.

Referring now to FIG. 5 b, an alternative embodiment is provided inwhich the image controller 530 is located on the body of the displaysubstrate. In FIG. 5 b, unless otherwise provided, like elements havebeen given like reference numerals. Unless otherwise provided, theprinciples of operation of the videoconferencing terminal of FIG. 5 bare similar to those of the terminal of FIG. 5 a, for which furtherdescription is considered not necessary.

The videoconferencing terminal of FIG. 5 b differs from that of FIG. 5 ain that commands may be transmitted from the image controller 530 by wayof a radio link. A radio transmitter 561 may be located at a convenientlocation on the display substrate 510. Preferably the radio transmitter561 is located at a central location relative to the display substrate510 as shown in FIG. 5 b. Furthermore, a radio receiver 581 is locatedat a convenient location so as to receive a radio signal 571 transmittedfrom the radio transmitter 561. Upon receiving the radio signal 571, theradio receiver 581 may then convert the received signal into appropriatesignal formats, e.g. an electric signal, which may be used for anyadjustments required in the speed of rotation of the actuator 540 or thetransmission rate of the display data.

Commands generated by the image controller 530 may be converted intoradio signals by known means such as for example an antenna. Similar tothe embodiment of FIG. 5 a, a storage unit with similar functionalitiesmay also be used in the embodiment of FIG. 5 b.

In some embodiments, where the image controller is mounted on thedisplay substrate 510, the use of an optical link or a radio link totransmit the commands to parts of the system other than the displaysubstrate 510 (as described with reference to FIG. 5 a and FIG. 5 brespectively) may be avoided. This may be the case where a synchronousactuator, such as a synchronous electrical motor, is used which isconfigured to operate at a substantially constant nominal speed. Theimage controller may then generate commands to adjust the line datatransmission rate of the displayed image. The image controller may use adata storage unit (as one described with reference to FIG. 2, 3 or 4) inorder to generate or adjust the image (asynchronously with respect tothe speed of the display substrate) based on detection signals receivedfrom the proximity sensor which is also mounted on the displaysubstrate.

FIG. 6 illustrates flow diagram of an embodiment of a method 600 forimage stabilization in videoconferencing. A terminal as described hereinmay be used to perform the method. For the sake of briefness, thefollowing steps of the method 600 are described below.

At an initial stage, step 610, a display substrate is moved in a cyclicmovement over a viewing area displaying a display data. The displaysubstrate occupies less than an entirety of the viewing area.

In a step 620, a proximity sensor detects the proximity of the displaysubstrate as it moves during a cycle. As mentioned above, the proximitydetection may be made by optical means, i.e. an optical emitter and anoptical receiver configured to establish optical coupling, or bymagnetic means, i.e. a magnetic detection element and a magnetic boosterpiece.

In a step 630, the proximity sensor generates a detection signal upondetecting the proximity of the display substrate as described inprevious step 620.

In a step 640 a cycle time of the cyclic movement of the displaysubstrate is calculated. This is done by an image controller. Asmentioned above, the image controller may be located at a fixed positionor on the body of the display substrate. Also the cyclic movement of thedisplay substrate may be calculated depending on the specificconfiguration in each embodiment. For example in case of using opticalcoupling for proximity detection, depending on whether the opticalemitter is movable or fixed, the calculation may respectively correspondto the time elapsed between one optical coupling to a subsequent opticalcoupling or to the time elapsed from the blockage of one opticalcoupling to the blockage of a subsequent optical coupling. Preferablythe cycle time calculated may then be divided into a number of imagelines that form a complete screen of the image to be displayed. Theresulting value, so-called line-data, may then be compared to apredetermined target value which is one that is considered to provide anacceptable image display.

In a step 650, the image controller generates a control command. Asmentioned above, the control command in order to adjust either thetransmission rate of the display data to the display substrate, or themovement of the display substrate caused by the actuator is controlled.

In step 660, as a result of the control command generated by the imagecontroller to an appropriate element of the terminal (as describedbelow), one of the following actions may be performed:

-   -   upon transmitting the control command to a line data        transmission unit, the line data transmission unit may adjust        the transmission rate sent to the display substrate and as a        consequence, the display rate of the display substrate is        adjusted so as to display the image without, or substantially        free of, instability effects; or    -   upon transmitting the control command to a driving circuitry of        the actuator, the speed of the actuator is adjusted and, as a        consequence, the movement of the display substrate is adjusted        so as to display the image without, or substantially free of,        instability effects.

At least a portion of the above-described apparatuses and methods may beembodied in or performed by various conventional digital data processorsor computers, wherein the computers are programmed or store executableprograms of sequences of software instructions to perform one or more ofthe steps of the methods, e.g., steps of the method of FIG. 6. Thesoftware instructions of such programs may represent algorithms and beencoded in machine-executable form on non-transitory digital datastorage media, e.g., magnetic or optical disks, random-access memory(RAM), magnetic hard disks, flash memories, and/or read-only memory(ROM), to enable various types of digital data processors or computersto perform one, multiple or all of the steps of one or more of theabove-described methods, e.g., one or more of the steps of the method ofFIG. 6, or functions of the apparatuses described herein such as animage controller.

Certain embodiments disclosed herein further relate to computer storageproducts with a non-transitory computer-readable medium that haveprogram code thereon for performing various computer-implementedoperations that embody, for example, the image controller, or carry outat least some of the steps of the methods (e.g., the method 600 FIG. 6)set forth herein. Non-transitory used herein refers to allcomputer-readable media except for transitory, propagating signals.

The media and program code may be those specially designed andconstructed for the purposes of the invention, or they may be of thekind well known and available to those having skill in the computersoftware arts. Examples of non-transitory computer-readable mediainclude, but are not limited to: magnetic media such as hard disks,floppy disks, and magnetic tape; optical media such as CD-ROM disks;magneto-optical media such as floptical disks; and hardware devices thatare specially configured to store and execute program code, such as ROMand RAM devices. Examples of program code include both machine code,such as produced by a compiler, and files containing higher level codethat may be executed by the computer using an interpreter.

Those skilled in the art to which the application relates willappreciate that other and further additions, deletions, substitutionsand modifications may be made to the described embodiments. Additionalembodiments may include other specific terminal. The describedembodiments are to be considered in all respects as only illustrativeand not restrictive. In particular, the scope of the invention isindicated by the appended claims rather than by the description andfigures herein. The various embodiments may be combined as long as suchcombination is compatible and/or complimentary. All changes that comewithin the meaning and range of equivalency of the claims are to beembraced within their scope.

What is claimed is:
 1. An apparatus, comprising: a display substrateoccupying less than an entirety of a viewing area and configured todisplay data; an actuator configured to move the display substrate in acyclic movement over the viewing area; a proximity sensor assemblyconfigured to generate, at least once during a cycle of the movement ofthe display substrate, a detection signal; and an image controllerconfigured to receive the detection signal generated by the proximitysensor assembly, calculate a cycle time of the cyclic movement of thedisplay substrate and generate a command to control at least one of atransmission rate of the display data to the display substrate and themovement of the display substrate caused by the actuator.
 2. Theapparatus of claim 1, wherein the proximity sensor assembly comprises anoptical emitter and an optical receiver.
 3. The apparatus of claim 1,wherein the proximity sensor assembly comprises a magnetic detector anda magnetic booster piece.
 4. The apparatus of claim 1, wherein the imagecontroller is configured to divide the cycle time into a number ofradial image lines that form a complete screen of the image to bedisplayed.
 5. The apparatus of claim 1, wherein the image controller isconfigured for generating a command for a driving circuitry of theactuator, thereby causing the driving circuitry to adjust the speed ofthe actuator.
 6. The apparatus of claim 1, wherein the image controlleris configured for generating a command for a line data transmissionunit, thereby causing the line data transmission unit to adjust thetransmission rate sent to the display substrate.
 7. The apparatus ofclaim 1, wherein the image controller is located on the displaysubstrate.
 8. The apparatus of claim 7, wherein the image controller isconfigured to transmit a command using an optical link.
 9. The apparatusof claim 7, wherein the image controller is configured to transmit acommand using a radio link.
 10. The apparatus of claim 7, wherein theactuator is a synchronous actuator, and the image controller isconfigured to generate commands to adjust the line data transmissionrate of the displayed image using a data storage unit to generate saidcommand.
 11. The apparatus of claim 2, wherein the optical emittercomprises a plurality of sources of emission of optical signal.
 12. Theapparatus of claim 2, wherein the optical receiver comprises a pluralityof elements of reception of optical signal.
 13. The apparatus of claim1, wherein at least one optical emitter transmits feedback informationto at least one optical receiver.
 14. A method for image stabilizationin videoconferencing comprising: moving a display substrate in a cyclicmovement over a viewing area and displaying a display data, the displaysubstrate occupying less than an entirety of the viewing area;generating by a proximity sensor assembly, at least once during a cycleof the movement of the display substrate, a detection signal; receivingby an image controller the detection signal generated by the proximitysensor assembly; calculating a cycle time of the cyclic movement of thedisplay substrate; and controlling at least one of a transmission rateof the display data to the display substrate and the movement of thedisplay substrate caused by the actuator.
 15. The method of claim 14,wherein the optical receiver receives the optical signal during anoptical coupling period in which the movement of the display substratecauses the optical emitter to establish optical coupling with theoptical receiver.
 16. The method of claim 14, wherein the opticalreceiver receives the optical signal through an optical coupling pathuntil a time at which the display substrate moves to a position at whichit blocks the optical coupling path between the optical emitter and theoptical emitter.
 17. The method of claim 14, wherein the opticalreceiver generates a detection signal when the optical emitter moves toa position to establish optical coupling.
 18. The method of claim 14,wherein the optical receiver generates a detection signal until theoptical coupling is blocked by the display substrate.
 19. The method ofclaim 14, wherein the image controller generates a command fortransmission to a line data transmission unit, causing the line datatransmission unit to adjust the transmission rate sent to the displaysubstrate and thereby adjust the display rate of the display substrate.20. The method of claim 14, wherein the image controller generates acommand for transmission to a driving circuitry of the actuator, causingthe driving circuitry to adjust the speed of the actuator and thereby,adjust the movement of the display substrate.